Shooting for 400HP, Need Bigger Exhaust?

[CDW6212R]

Yes I am old school, I haven't been around much racing here other than 20 years ago when we used to go to our two 1/8 mile tracks a lot for a couple of years. I try to see what works for others and learn from it, as everyone does. But I also look for details that make a bigger difference than the popular common ideas or tricks.

I just spoke to a man yesterday who was part of the development of the KB kits on the Fox Mustangs, when they were using 1.5/1.7 and he said a 1.8 blower. Not commonly known, but they finally hit over 500rwhp in a Fox Mustang, without an intercooler, using the GT40 intake and KB plenum. The stock block didn't survive long after the project was done, but he said the biggest problem they had was the exhaust. They ended up with 1.75" long tube headers, no cats, and 2.5" dual pipes back to the bumper. I think they were constrained by the intention of KB for much of the engine and parts. The heads were Dart, and they had to push the blower rpm to get 16psi of boost, again without an intercooler. He said forcing the air in wasn't the problem, it was the high heat from the back pressure of the exhaust, and they had to over build the fuel system and pumps to get the A/F ratio rich enough to avoid detonation.

That was a big achievement back then for sure, but there aren't examples close to that since then, as I said about 400rwhp is the typical max hp you see from a KB on a Fox Mustang. The exceptions were the custom A2A IC's that were added by welding the KB plenum to divert the airflow out the left side, and eventually back into the plenum above the GT40 lower side.

What I learned from that expert conversation was that the 2.2 blower is not likely to push 500hp at good blower rpm, and I'm not going to make it run 18,000rpm(the recommended limit). I want it down in the low teens, 12-13,000 rpm at the shift point I think would last a long time. Given what KB makes, that leaves the 2.6 size for me, so hopefully I can retire and start this Fall.

 

[Blown]

These are old school rigs, with enough to tune electronically. I wish you success n getting to retirement and the build. I may be about 5 years behind you, hopefully less, but then would be the time, having the time to do a build an awesome build.

I have read that these blocks can, "Saw themselves apart" with big, big power.


The Tweecer test bed below, a 93 Stang, 331 stroker, Pro turbo, 11lbs, with, of course, Tweecer tuning. That's from a starting point of 300hp and 330ftlbs before the boost, 200hp added with 11lbs. 18horses per lbs is on the higher end of efficiency.

 

[CDW6212R]

A turbo is the best way to go if it can be made to fit. I wanted one, but I didn't like the compromises it would require in the engine bay and routing the piping.

 

[Blown]

Yup, still not fully accepting new CO emissions. It is not so bad to be stuck around 350hp and 410ftlbs of torque. I may do some cat work when I can, larger muffler(s), and larger tail pipe(s) to get closer to 400. The headers actually do not seem to be the limiting factor up to around 380 to 400hp with the stock cam. Any bigger cam starts pushing these headers.

I have a 15" Glass Pack coming to add behind the muffler as I want it a bit quieter. I am sure the recently installed Flowmonster is flowing better than the turbo muffler I had on it, but it is considerably louder.

 

[Blown]

View attachment 439138

Here is the Dyno sheet for my AWD after the Xpipe, exhaust and cats magic but before the blower rebuild.

Will have another Dyno sheet for after the rebuild and going back to the 2.86 pulley

I hope you get 400 or better and am looking forward to what it does.

 

[CDW6212R]

Yup, still not fully accepting new CO emissions. It is not so bad to be stuck around 350hp and 410ftlbs of torque. I may do some cat work when I can, larger muffler(s), and larger tail pipe(s) to get to closer to 400 but the headers would be the limiting factor then.............................Perhaps 380HP?

I have a 15" Glass Pack coming to add behind the muffler as I want it a bit quieter. I am sure the recently installed Flowmonster is flowing better than the turbo muffler I had on it, but it is considerably louder.

Those Flowmonsters were just on a clearance sale for pennies, $50 for a pair etc, but they sold out fast. I'm thinking of taking a shot at building a resonator after I do the mufflers. OEM mufflers all have a dead chamber inside, that's why they are so much quieter. I don't know of a method to calculate the size needed to be effective, I might just toss one together and see how it does(small, 6x8x3" maybe).

 

[Blown]

To Summarize, I do need more exhaust work for 400hp!

For now, The maximum I am going to try to push the current exhaust to is 8lbs and 376hp/446flbs of torque. I tried a bit over 9lbs and it seemed a bit constipated and it should have been based on the calcs. I screwed-up as my background was more F150/Bronco with larger headers and exhaust.

I am running:
1.5" headers/primaries, TMH's. The header calc. show primaries of 1.42" diameter. 2.2CFM Ex.Gas X(376hp/8cylinders= 103CFM 1.5" pipe will flow max 171CFM.

The Collector calc. shows the need for 2.60" downs at 6lbs and 2.74" at 8lbs. The stock downs are 2 1/4", 2.2CFM(ExGas per hp) X (376hp/2downs)= 414CFM and 2 1/4" pipes flow up to 408CFM.

The 3" single muffler and tailpipe should be a little larger. 2.2CFM X 376hp= 827cfm. A 3" flows 747CFM. Little losses here at high rpm but I think the cats, muffler and tight bends have already slowed exhaust before it hits the 3", so it will work.

To get to 400, It needs cat work, larger muffler(s), and larger tail pipe(s) (if dual, a crossover). I estimate $500 if I do it myself. For $500 and my labor, I am not sure 25hp is enough. I will see how I running 8lbs works first, what Muscle Junkie Jim's results are and then make a decision.

 

[CDW6212R]

That is a thoughtful set of expectations. It's hard to pin down reality versus the theory and math calculations. I also have no personal examples, but the countless forum examples tell me the solution is somewhere among the ideas we have posted here.

 

[Blown]

After more research, I think 350 is realistic and 375 is pushing it with the headers and downpipes...........It would be nice to get to a dyno without spending more.

 

[Blown]

I revisited the web site I posted about header size calculations utilizing, engine inputs, cam and rpm. I updated that post which is on page two

My mistake was that I had input "duration" not "advertised duration" for the stock cam exhaust. The primary header size with the stock cam and around 6lbs/VE of 130 in my build went to 1.5". It was previously showing like 1.36". At what would be 9lb/VE155 on my build, primary size jumps to 1.58" or 1 5/8" headers................................The collector diameters increased as well to 2.60" and 2.74" This is why I have revised my numbers in the post above down to 350 to 376hp. Musclejunkie Jim's build is at 300 to the wheels which is 360-375 at the crank. That's with TMH's, but with better flow than my build from cats-back. I would be pleasantly surprised if he is able to get up to 400 and would know what to do to get there myself.

Primary's Diameter
Cams Stock E303
VE130 1.5" 1.58"
VE155 1.58" 1.66"

 

[MuscleJunkie]

Has anyone come up with a “real” documented driveline HP/Torque loss on the 2nd Gen Explorer 5.0 automatic and AWD. Lots of numbers thrown around (12-25% or more) but nothing that has seemed backed up by facts…

 

[Blown]

My case study of one and it's ugly, like 25%.

One case study, a Stock 98 5.0 4X4 Dyno's at 157.7hp and rates 210 at the Crank.

From TMH site:

 

[MuscleJunkie]

Ugly like as in 25%. One case study, a Stock 98 5.0 4X4 Dyno's at 157.7hp and rates 210 at the Crank.

From TMH site:

View attachment 439501

I’ve seen this one and didn’t he say it was a 4x4 truck? Would it be even more on AWD or the same?

 

[Josh P]

I’ve seen this one and didn’t he say it was a 2WD truck? So would it be even more on AWD?

96 was 210 hp and in 97 it got bumped to 215 hp. The bigger parasitic loss is the 288 lb/ft torque dropping to 203 at the wheels

 

[Blown]

The 4X4 would be a bit less as I am sure it was not pushing the front wheels when tested like an AWD would.

It is also a 1998 tested in 2004 and may not have been in the best tune.

I want to go with 22% cause I don't want to lose toooooooo much, ha!

I have also given myself a few more horses before boost. I figure 250hp and 328ftlbs to start with (Headers+20, Exhaust work+10, Elec Fan+5, 75mm T-Body and 91 Octane)..........................I am making my calcs based on 16hp/lb boost since the exhaust is tight.

 

[Fix4Dirt]

im pretty sure awd would lose a bit more than 4wd, since as blown said running in rwd and the 4404s from what limited knowledge i have are not quite a direct drive to rear so to speak, since when the case wears it has been known to roll back in park

 

[CDW6212R]

My case study of one and it's ugly, like 25%.

One case study, a Stock 98 5.0 4X4 Dyno's at 157.7hp and rates 210 at the Crank.

From TMH site:

View attachment 439501

I think that 25% estimate is likely very close in the real world. I'd bet at least 10% of it is from the exhaust, and the losses go up as the power goes up, at an increasing rate. The stock exhaust is at a guess killing a good 20hp, but if you can reach 350hp, the loss will be much more, say pushing 50hp(versus stock).

 

[Blown]

It's Ugly I tell ya, and always seems I am driving uphill, at altitude with a headwind here, and then CARB!

Time to move away from emissions, Go with 11lbs of boost, get bigger heads, make bigger headers, add 2 3/4" downs with high flow cats, crossover, big mufflers, 2 1/2 tail pipes...................................

I enjoy this stuff, have beaten this to death, but have found some answers, thanks!

I am done with 9+lbs boost with this exhaust. I am going to see what 8lbs feels like for fun and am running 6lbs very well.

 

[CDW6212R]

From what I learned from that developer person I mentioned about the old Fox Mustang KB system; I think Explorer owners should invest a lot more into the exhaust, and much less elsewhere, when they have boost. The boost can force plenty of air into even mild flow induction parts(HCI etc), but expelling the air is a big problem when the factory system is so restrictive.

I could have saved a little money on my intake and heads that I got almost three years ago. It was easier aiming at higher flowing induction parts, because they do exist at least. The exhaust we have learned doesn't exist, you have to make it somehow. So don't go overboard with heads and intake just yet, not until you do know that you can make the good exhaust happen.

 

[Blown]

I am not changing anything but for adding a 3" X 15" long glass pack muffler to quiet and restrict it more.

I need to turn my attention to make sure she can be emissions ready by July. I need to have, 'at the ready', a stock airbox, throttle body, tubing, and a tune. I tossed all that crap.